Several ring-substituted 1-dialkylaminoalkylthioxanthenones were prepared and submitted for antitumor activity. In addition hycanthone N-methylcarbamate was prepared and submitted for antitumor action. If this drug behaves like Mitomycin C in the sense that it can serve as an alkylating agent for DNA then the compound should intercalate first and then monoalkylate a DNA base. Theoretical studies of intercalation complexes and computerized drug design have resulted in (1) the determination of possible conformations of intercalation sites; (2) a theoretical justification of the exclusion principle; (3) the manner in which chromophores fit into the intercalation site and substituents bind to the backbone and (4) an explanation of base pair specificity. Based on the shape of the intercalation site, molecules which fit well are being designed, their binding energies are being computed and recommendations are being made for synthesis with the goal of correlating antitumor activity with theoretical binding energies and other parameters.